Ozone (O3) is a powerful disinfectant with many industrial and commercial applications. For example, ozone is used to oxidize organic contaminants from drinking water, including the naturally occurring taste- and odor-causing compounds. Ozone is also used in the effluent from the secondary treatment of wastewater to remove trace organic contaminants and endocrine disrupting compounds (EDCs) from the water before reuse as indirect potable water or discharge to a water body.
Ozone gas (O3) is commonly produced in a corona discharge-based generator from air or high-purity oxygen (O2). For larger ozone needs, oxygen is generally the less expensive option for a source gas. The conversion of oxygen into ozone in commercial corona discharge generators is typically between 3 and 14%, and in certain applications the resulting oxygen-ozone mixture is provided as a product directly to the downstream user without further treatment.
It has been found that ozone may also be used to enhance anaerobic digestion by converting difficult to biodegrade compounds into more easily biodegradable compounds. Ozone may be used in this way to enhance biogas production from anaerobic digestion. For anaerobic digestion of sludge, it is theorized that the ozone lyses the cell membranes, thereby exposing the more easily biodegradable cytoplasm of the bacteria. Fermentation waste, often called vinasse, can contain compounds such as phenols that are toxic to the anaerobic bacteria and other larger carbon-based compounds that are recalcitrant. Pretreating this feed with ozone will reduce or eliminate the toxic compounds and make the larger compounds more biodegradable, thereby reducing the required residence time in the digester. In an anaerobic digestion process, it is undesirable to have excess oxygen present because the oxygen reduces the methane (CH4) yield by promoting aerobic digestion.
Accordingly, there is a need for an improved method of recovering unreacted oxygen from an ozone-generation process so that the effluent may be efficiently used for an anaerobic digestion process, while maintaining high efficiency in the ozone-generation system.